Stepping assembly and circuit

ABSTRACT

An intervalometer uses a rotary switch mounted to a base through shafts which maintain concentricity. An offset stepping mechanism drives the switch under control of a drive energizing circuit having interrupter contacts on the switch. A load energizing circuit includes additional contacts on the switch for sequentially energizing a plurality of independent loads, while shunting all nonenergized loads. Separate switch sections separate the drive energizing circuit from the load energizing circuit. When the switch is in a home position, it must be manually rotated to another position before automatic sequential stepping can occur.

I United States Patent 1 1 3,582,579

[72] lnventors Frederick M. Ford [56] References Cited g 'g lm C UNFTEDSTATES PATENTS I 21 1 App] No 12;: 3,384,728 5/1968 Davis ZOO/168(8)[221 Filed May 22,1969 3,405,376 10/1968 G1ese,Jr. et al. 335/138 [45]Patented June 1, 197] Primary Examiner-Robert K. Schaefer [73] AssigneeOak Electro Netics Corporation Assistant ExaminerJ. R. ScottAttorney-l-lofgren, Wegner, Allen, Stellman & McCord ABSTRACT: Anintervalometer uses a rotary switch mounted to a base through shaftswhich maintain concentricity. An offset stepping mechanism drives theswitch under control of a [54] AND CIRCUIT drive energizing circuithaving interrupter contacts on the switch. A load energizing circuitincludes additional contacts [52] US. Cl 200/18, on the switch forsequentially energizing a plurality of inde- 200/ 1688, 335/138 pendentloads, while shunting all nonenergized loads. [51) Int. Cl H01h 3/00Separate switch sections separate the drive energizing circuit [50]Field of Search 200/14, 18, from the load energizing circuit. When theswitch is in a home 38, 168 (S); 335/123, 140, 228, 272, 138; 74/26,position, it must be manually rotated to another position be- 575 foreautomatic sequential stepping can occur.

PATENTED Jun 1 197:

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STEPPING ASSEMBLY AND CIRCUIT This invention relates to an assembly andcircuit for timing intervals, and more particularly to an improvedstepping assembly and circuit therefore.

lntervalometers are devices which provide a series of timed electricalpulses, often coupled to separate loads. When limited mounting height isavailable, it has been known to use an intervalometer in which a rotaryswitch and a stepping motor are each mounted to a base, on offset axes.A link traversing the axes converts movement of the stepping motor intoa reciprocating motion which stepwise drives the rotary switch throughits positions. At each position, connection is made through electricalcontacts to the loads associated therewith. lnterrupter contacts carriedby the switch control a self-completing circuit for energizing thestepping motor in order to cause the switch to automatically stepthrough all of its positions. Many such assemblies of the above natureare known, an example of which is shown in a patent to Giese, Jr. et al.No. 3,405,376.

Prior rotary stepping assemblies and circuits of the nature describedabove have several disadvantages which greatly limit their use. Theloads which are to be energized by intervalometers are often explosivedevices, in which it is absolutely essential that accidentalenergization of the loads be precluded, both when connecting the loadsto the switching assembly and during energization of other loads. Priorcircuits have not precluded accidental load energization, which couldoccur by accidental electrical actuation of the triggering circuit whilepersonnel are connecting the loads to the circuit. Applicants circuitovercomes this problem by precluding electrical actuation until manualactuation of the switch enables the electrical circuit.

Another type of accidental load energization which prior circuits haveallowed occurs when electrical noise or the like is coupled to theloads, resulting in false triggering. Other types of failure occur whena load is defective and short circuits the self-stepping drive circuit.In such an instance, the stepping circuit is rendered ineffective, andthe remaining loads are not energized. It would be'desirable that anydefective load should be bypassed by the switching assembly and circuit,allowing further loads to be energized. The applicants circuit andassembly overcomes all of the above disadvantages.

The mechanical construction of prior stepping assemblies has also beenunsatisfactory with respect to maintaining concentricity and long lifeof operation. When plural switch sections are required, the resultingstack height requires that the concentricity of the rotary switchassembly be maintained within close tolerances. Typical prior switchingassemblies using screws inserted through the stack and threaded into abaseplate do not have the stability necessary to maintain the desireddegree of concentricity. Prior rotor bearings have also required anunnecessarily large amount of space and have been costly. These andother disadvantages of prior rotary stepping assembles have beenovercome by the improved stepping assembly also disclosed herein.

One object of this invention is the provision of an improved steppingassembly and circuit therefore.

Another object of this invention is the provision of an improvedstepping assembly and circuit for sequentially energizing one load at atime, while maintaining a shorted connection across all nonenergizedloads. One feature of the circuit is that it includes means forbypassing defective loads and means for preventing accidental electricalactuation by first requiring mechanical actuation of the steppingassembly.

Still another object of this invention is the provision of a rotarystepping assembly having improved concentricity for multiple switchsections. Some features of the improved switching assembly includeimproved bearing means, an integral pointer for indicating switchposition and allowing manual actuation, and other improved design.

Further features and advantages of the invention will be apparent fromthe following specification, and from the .drawings, in which:

FIG. I is an exploded perspective view of the stepping assembly;

FIG. 2 is a top plan view of the assembly of FIG. I;

FIG. 3 is a side plan view, partly in section, taken along lines 33 ofFIG. 2;

FIG. 4 is a fragmentary sectional view taken along lines 4-4 of FIG. 3',

FIG. 5 is an upward looking plan view of the bottom face of the upperswitch section, taken along lines 5-5 of FIG. I; and

FIG. 6 is a schematic diagram of the circuit for the switching assembly.

While an illustrative embodiment of the invention is shown in thedrawings and will be described in detail herein, the invention issusceptible of embodiment in many different forms and it should beunderstood that the present disclosure is to be considered as anexemplification of the principles of the invention and is not intendedto limit the invention to the embodiment illustrated. The scope of theinvention will be pointed out in the appended claims.

Turning to FIGS. I3, the improved stepping assembly is illustrated indetail. The assembly includes a stepping motor, such as a reciprocaldriving assembly 10 which when energized rotates a plate member II abouta longitudinal shaft axis 13. The motion in plate II is used to stepwisemove a driven rotary switching assembly 15, illustrated-in exploded viewin FIG. 1. Switching assembly 15 rotates about a longitudinallyextending rotor shaft I7 which is generally parallel with respect to themotor shaft l3. When minimum stack height is desired, the axes of motorshaft 13 and rotor shaft 17 may be offset, as illustrated in thedrawings. Both motor assembly 10 .and switching assembly 15 are mountedto a base assembly 20 of improved construction, as will appear. If stackheight is no problem, the switching assembly may be axially aligned withthe motor assembly and connected through a common shaft, while stillretaining the advantages of the circuit and many of the advantages ofthe improved construction disclosed herein.

When the assemblies are offset, as illustrated, an actuator link 22spans the distance generally between the driving and driven assemblies,and is spaced from the axes of motor shaft 13 and rotor shaft I7.Driving assembly 10 moves plate 11 along a limited arcuate path during apower stroke, when assembly I0 is energized. This movement causes linkactuator 22 to be longitudinallydisplaced generally to the right in thedrawings, causing stepwise rotation of switching assembly 15. As willappear, switching movement opens the energizing circuit for drivingassembly 10. A spring 23 thereafter returns the link 22 to its restposition, after which the stepping cycle of operation is repeated by aself-completing energizing circuit, to be described later.

Driving assembly 10 may be any conventional assembly for producing alimited distance movement or a steptype movement. The details of drivingassembly 10 form no part of the present invention, and will only brieflybe described with referenceto one type of. mechanism suitable for thepurpose, namely, a rotary solenoid. The solenoid is fixedly mounted to.the base 20 bya screw 24, FIG. 3. When a solenoid coil 25,

FIG. 3, is energized, the rotary solenoid pulls plate 11 downwardlytoward the coil 25. A plurality of inclined surfaces or races 27 aredisposed on plate 11. Each race 27 includes a ball 28 trapped betweenthe race and the surface of the solenoid. Upon actuation, the ball andrace combination transforms the downward pull of the solenoid into acombined rotary and slight axial movement of plate 11.

Link 22 is pivotally connected to plate II by a stud and lockring 29which passes through an aperture in link 22 and is threaded into plateI]. The link 22 is longitudinally movably mounted to plate 20 by a guideplate 3I riveted to plate 20. Guide 31 includes an aperture throughwhich the slide 33 of link 22 extends. The guide surface defining theaperture forms a bearing for slide 33.

When coil 25 is energized, plate 11 rotates counterclockwise, causingslide 33 to be longitudinally moved generally to the right in both FIGS.1 and 2. Spring return 63,

trapped between an outer end portion 35 of slide 33 and the guide 31, iscompressed upon energization of the rotary solenoid. As will appear, thestepwise movement of the switching assembly 15 deenergizes solenoid coil25. Compressed spring 23 now expands and returns slide 33 to its restposition, thereby completing one cycle of movement.

Switching assembly 15 consists of a first switch section 37 and a secondswitch section 39. The pair of sections 37 and 39 respectively controlthe energization of the load and the energization of the stepping motor10. Each switch section 37 and 39 includes a stator which is fixed withrespect to base 20, and a rotor affixed to rotor shaft 17 and whichmoves with respect to base 20.

Switch section 37 includes an insulated stator wafer 40 which mounts aplurality of electrical contacts, only a few of which are illustrated inFIG. 1. Certain of these contacts (labeled 42) are associated with theloads, with each contact 42 corresponding to a different load. Anelectrical contact 43, FIG. 2 (and FIGS. and 6), not associated with anyload, is used to form a home position for the rotary switch. As willappear, wafer 40 includes other contacts, some of which are located onthe bottom side of the wafer.

For making connection to the fixed stator electrical contacts, a rotor45, movable with respect to stator wafer 40, includes a rotor wafer 47with an integral indicator 48 protruding upwardly therefrom. The bottomside of wafer 47 has a slot into which the rotor shaft 17 extends, seeFIG. 3, for fixedly mounting rotor wafer 47 with respect to the rotorshaft 17. Rotor wafer 47 is fixedly connected to electrical contactsaligned for various circuit connection with the stator contacts at eachstepwise rotational position of the rotary switch. The exactconfiguration of the rotary electrical contacts will be described later.

Switch section 39 includes an insulated stator wafer 50 mounting a pairof stator electrical contacts 52 and 53. A rotor wafer 55 is locatedwithin a central aperture in wafer 50, and has rotor contacts alignedfor various circuit connection with the stator contacts. The rotor shaft17 is press-fit within an aperture in wafer 55, for rotational movementof the rotor contacts, the details of which are described later. Thecross section of rotor shaft 17 is noncircular and corresponds to theshape of the aperture in rotor wafer 55, and with the shape of the slotwithin rotor aperture 47, for causing both rotor wafers 47 and 55 torotate with rotor shaft 17.

The switching assembly includes means for converting the generallyreciprocating motion of plate 11 and link 22 into corresponding stepwiserotation of rotor shaft 17. A ratchet plate 60, affixed to the lowerportion of rotor shaft 17, has a plurality of teeth 61 struck upwardlyfrom the plane of the ratchet plate. The teeth 61 are axially inclinedand spaced about the periphery of the ratchet 60. Slide 33 of link 22carries a downwardly disposed pawl 63 which is located adjacent a pairof the ratchet teeth 61. As the slide 33 is moved to the right asillustrated in the drawings, pawl 63 pushes against one of the upwardlyextending teeth 61, rotating the ratchet 60 counterclockwise about rotoraxis 17.

In order to detent the stepwise rotor motion, ratchet 60 includes aplurality of apertures 65 disposed on the upper face of the ratchetplate. A lead spring 67, located immediately above ratchet 60, has apair of detents 68 struck downwardly for engagement in a pair ofcorresponding apertures 65 in the ratchet plate. As the rotor solenoidis energized, the move ment of slide 33 and hence pawl 63 is transmittedthrough one of teeth 61 to the ratchet plate 60, causing the detents 68to be forced upwardlyout of their corresponding apertures 65. At the endof the power stroke, the detents 68 are urged downwardly into the nextpair of apertures 65, thereby detenting the rotary switch to the nextswitch position. Thereafter, spring 22 urges slide 33 to the left,causing the pawl 63 to ride up and over the next tooth 61 and snap intoplace behind the tooth, for subsequent pushing motion against the toothupon the occurrence of the next power stroke.

During each cycle of stepwise rotation, an interrupter assembly 70 isactuated and changes the state of an electrical switch in order tocontrol energization of the rotary solenoid. lnterrupter assembly 70,see especially FIG. 4, is mounted on an insulated stator plate'71 whichcarries a fixed electrical contact 73, a movable spring contact 74, anda further fixed contact 75. The contacts 73, 74 and 75 form asingle-pole, double-throw switch, with spring contact 74 normallyresting against contact 73. Upon actuation, spring contact 74 is firsturged out of engagement with contact 73, and then into engagement withcontact 75.

For actuating the switch, a part of the spring contact 74 is bent intoan outwardly extending, generally V-shaped shoulder 80, which isdisposed radially inward with respect to rotor shaft 17. Shoulder isengaged by a cam assembly 85, FIG. 1, located on the same switch planeas interrupter assembly 70. Movement of cam assembly is controlled by anupwardly extending finger 83 from slide 33. The cam assembly includes anextending head 86 located adjacent shoulder 80 of spring contact 74, asseen best in FIG. 4. The cam 85 also includes a pair of legs 88 and 89which extend radially outward and bridge finger 83 of slide 33.

For rotatably mounting cam 85 to the switch assembly, a plate 90,disposed below the cam, includes an upwardly extending extruded wall 91having a diameter slightly smaller than the diameter of a circularaperture in cam 85, defined by a surrounding wall 93. Extruded wall 91forms a bearing for wall 93. To reduce friction, a plurality of balls 95are pressfit into apertures extending through cam 85, for sliding movement over the upper face of plate 90. A cam spring 96 biases balls 95against the upper face of plate 90.

The operation of the interrupter assembly may be seen best with respectto FIG. 4. When slide 33 is in its rest position, finger 83 restsagainst shoulder 88, causing the head 86 ofcam assembly 85 to be spacedfrom shoulder 80 of spring contact 74. As slide 33 is moved to theright, by reason of actuation of the rotary solenoid, rotor shaft 17begins to turn due to the action of the pawl and ratchet mechanismpreviously explained. However, the cam assembly is still at rest becausethe space between shoulders 88 and 89 is greater than the width offinger 83.

Near the end of the power stroke of slide 33, finger 83 engages shoulder89 and subsequent movement of slide 33 is transmitted through finger 83against shoulder 89 to cause rotation of the cam assembly. This causeshead 86 to be rotated against shoulder 80, lifting the spring contact 74out of engagement with contact 73 and into engagement with contact 75.As will appear, opening of contacts 73, 74 removes power from the rotarysolenoid, allowing spring 23 to return slide 33 to its rest position.Near the end of this return stroke, finger 83 again contacts shoulder88, moving cam assembly 85 in a clockwise direction and moving head 86out of engagement with shoulder 80. The spring biasing of contact 74causes the contact to move out of engagement with contact 75 and intoengagement with contact 73, returning the interrupter assembly to itsrest state.

In order to stack the switching assembly 15 into a single unit, andmaintain all parts concentric with respect to rotor shaft 17, animproved mounting structure is utilized. Base 20 includes a pair ofelongated shafts 100 and 100' which are permanently affixed to base 100,as by riveting, and extend upwardly therefrom. For clarity, only shaft100 and the parts of the rotor assembly coacting therewith will bedescribed in detail, it being understood that the same disclosureapplies to shaft 100. Elements for shaft 100' which correspond tosimilar elements for shaft 100 are identified by the same referencenumber followed by a prime While two mounting shafts have beenillustrated, additional shafts may be provided for switching assembly15, if desired.

Shaft 100 includes a portion of reduced diameter, starting a shortdistance above plate 20 and extending upwardly therefrom for theremaining distance. A transverse shoulder surface 102, which joins thereduced diameter portion with the lower shaft portion, forms one of themounting or clamping surfaces for the stator portion of switchingassembly 15. The upstanding shaft terminates at its upper end in a guidesurface 103 such as a screw. This surface is adapted to guide and engagea fastening means, such as a spanner nut 105 which is threaded over thescrew. The bottom plane surface 106, FIG. 3, of spanner nut 105 abutsand forms the upper mounting surface for the stator portion of switchingassembly 15.

Various stator portions of the switching assembly have aligned apertureswhich define a pair of hollow channels through which shafts 100 and 100extend. The nuts 105 and 105' are screwed down to clamp the statorsections in a predetermined order against the base 20. Of course, theparticular order of the stator sections is generally immaterial, andgroups of coating sections may be placed at different stack heights, asdesired.

As seen best in FIG. 1, the clamped stator sections have eitherapertures or bifurcated fingers which completely or par- .tiallysurround shafts 100 and 100'. Apertures are used for one end of spring67., stator 71, plate 90, wafter 50 and wafer 40, and bifurcated fingersare used for the opposite end of spring 67, and spring 90. A spacer 110is located between plate 91 and wafer 50, and a spacer 112 is locatedbetween wafer 50 and wafer 40, to provide clearance between thecorresponding switch sections.

After all of the switch sections are stacked in the desired order,spanner nuts 105 and 105' are threaded onto screws '103 and 103,respectively, clamping the stator portions of the .switch betweenshoulder 102 and the bottom surface 106 of the spanner nuts 105. In thepresent embodiment, the lower surface of plate 71 rather than the lowersurface of spring 67 forms the stator abutment with shoulder 102,because the clamped stator assembly. The end of rotor shaft 17 adjacentplate 20 has a circular cross section, and is enlarged with respect tothe remaining portion of the shaft, as seen best in .FIG. 3. Enlargedportion 120 is joumaled within the circular aperture of a boss 122upstanding from base plate 20. The whole thickness of the boss plateserves as a bearing surface for the enlarged portion 120 of the rotorshaft 17, without requiring the rotor shaft to extend beyond the flatplane of the bottom surface of plate 20. As seen in FIG. 3, thisconstruction allows a tolerance in which a portion of the rotor shaftmay extend beyond the bottom surface of the bearing, but insufficientlyfar to extend beyond the flat plane defined by the lower surface ofplate 20. The upper surface of the boss forms a bearing against whichthe ratchet plate 60 abuts for rotational movement.

The upper end of rotor shaft 17 is press-fit into the slot formed inrotor wafer 47. As seen in FIGS. 2 and 3, wafer 47 has an integrallyformed indicator 48, which may be in the shape of .an arrow, in order tovisually indicate the position of 1 the rotary switch. If desired,indicator 48 may extend through an aperture in a housing (notillustrated) for an intervalometer using the illustrated steppingassembly, in order to visually indicate rotor switch position. Aportion'of the rotor wafer 47 includes a screwdriver slot 125, formanually rotating the rotor assembly independent of the rotary solenoid.As will be explained, manual actuation is necessary before the steppingcircuit allows automatic, self-completing electrical actuation of therotary solenoid.

The circuit for the switching assembly will now be described in detail,along with a detailed description of the switch sections 37 and 39. Asseen in FIG. 6, a plurality of loads L1 I through L-l0 are to beindividually, sequentially energized by the potential difference acrossa source 130 of DC voltage.

The potential difference is available from a positive potential line 131and a negative potential line which is connected to a source ofreference potential or ground 132. While DC source has been illustratedas supplying a single DC voltage to line 131, it will be recognized thatany number of DC voltages may be available therefrom, depending upon therequirements of different loads and/or the stepping motor coil 25.

All loads Ll through L-10 have individual first terminals 135 connectedin common to ground 132, and a second or energizing terminal 136connected through individual lines to a corresponding stator loadcontact 42 on the upper face 37U of switch section 37. In addition tothe 10 stator contacts 42, a home position contact 43 and an additionalactivate contact 140 are also mounted on the upper face 37U, providing atotal of twelve equally spaced stator contacts. The home stator contact43 and the activate stator contact 140 are both coupled directly toground 132.

For connection to the stator contacts, the rotor on upper face 37Uconsists ofa first element or short ring segment 142, connected to onlya single of the stator contacts at any one time, and a second element orring segment 144 which is common to all of the remaining statorcontacts. Rings 142 and 144, electrically insulated from each other, aremechanically affixed to the rotor wafer 47 and rotate with movement ofthe rotor shaft.

The lower face 37L of switch section 37 also contains stator and rotorparts. The ring segment 142 on upper face 37U has a pair of contiguouselectrical leads 142' which extends through the insulated rotor wafer 47and electrically connect to a circular rotor ring on face 37L. Ring 150has an arcuate section 151 of reduced radial diameter. A single statorcontact 153 has a length which continuously contacts rotor ring 150except when the segment 151 is located adjacent thereto. Contact 153 isdirectly connected to the normally open contact 75 of interrupter switchassembly 70. It should be understood that the lower face 37L in FIG. 6is being viewed from the top, with wafer 40 being broken away so thatonly the rotor ring 150, wafer 47 and stator contact 153 areillustrated. Therefore, as viewed in FIG. 6, as the rotor on the upperface 37U is rotated counterclockwise, the rotor on the lower. face 37Lis similarly rotated counterclockwise. 7

Switch section 39 has a continuous rotor ring 157 which is mechanicallyconnected for rotation with rotor wafer 55. Ring .157 includes anarcuate section 158 of reduced radial diameter, extending over an arccorresponding to one stator contact position. Stator contact 52 has ashort radial length which con tinuously contacts ring 157 except whensegment 158 is located adjacent thereto. Stator contact 53 has a longradial length which continuously contacts ring 157, including whensegment 158 is located adjacent thereto.

Switch section 39 forms a part of the circuit which generally controlsenergization of coil 25 for controlling the stepping movement of theswitching assembly. This section is electrically separate from thecircuits associated with switch section 37, which control energizationof the loads L1 through L-10, as will be explained. Stator contact 52 ofswitch section 39 is directly electrically connected to the normallyclosed contact 73 of the interrupter switch 70. The spring contact 74 ofthe interrupter switch is electrically connected through a singlepole,single-throw switch 166 to positive lead 131. A singlepole, single-throwswitch 161 shunts contacts 73 and 74. To complete the solenoidenergizing circuit, stator contact 53 is connected to one side of coil25, the other side of which is directly connected to ground 132.

In operation, switch 166 is closed when the stepping assembly andcircuit are to be operative. Switch 161'when open allows an operator toselect automatic, and when closed'to select manual sequential actuationof the loads. The operation will first be described for automaticoperation, i.c., switch 161 remains open at all times.

When the switching assembly is in its home position, as illustrated,rotor segment 142 is electrically connected to home contact 43. At thistime, ground is shunted across terminals 135 and 136 of all loads L-1through L-10, by means of the direct connection from terminals 135 toground 132, and by means of terminals 136 being connected to common ring144, which is connected through stator contact 140 to ground 132.

The rotor segment 142 is also grounded by home contact 43 which isdirectly connected to ground 132. This grounds ring 150 via leads 142;however, this has no immediate effect because segment 151 is adjacentand hence spaced from contact 153. Electrical actuation of the switchingassembly is not possible at the home switch position, because no sourceof power can be connected to coil 25. Even if switch 166 is closed, thepower connection through contacts 73, 74 to stator contact 52 has noeffect because segment 158 is located adjacent and hence spaced fromstator contact 52.

The home position described above represents a safety condition in whichaccidental electrical actuation of the stepping assembly and/orenergization of the loads is precluded. Personnel can safely connectloads, such as explosives, into the circuit at this time without thepossibility of accidental electrical actuation, even by stray electricalfield pickup, because the loads are all shorted across ground. Toactivate the electric circuit for subsequent operation, it is necessaryto manually rotate the rotor out of its detented home position and tothe next detented or activate position, at which segment 142 contactsactivate contact 140. In the activate position, home contact 43 contactscommon ring 144, thus maintaining ground across all loads. Also, contact153 remains disconnected from ring 150 because a portion of segment 151is still located adjacent thereto.

Manual rotation to the second or activate switch position causes ring157 on section 39 to rotate adjacent and connect with contact 52,thereby connecting coil 25 to normally closed contact 73 of interruptingswitch assembly 70. When electric power is applied to the system byclosing of switch 166, automatic self-completing energization of thecircuit is initiated. More particularly, positive potential from line131 is connected to coil 25, energizing the rotary solenoid. Theresulting power stroke stepwise rotates the rotor shaft one position andcauses ring segment 142 on face 37U to rotate adjacent stator contact 42associated with load L-l. Also, ring 150 on face 37L is rotated incontact with stator contact 153, connecting ring segment 142 via leads142', ring 150 and stator contact 153 to normally open contact 75 of theinterrupter switch 70. All other loads L-2 through L-10 are maintainedshunted across ground, because common ring 144 is connected to ground132 via both home contact 143 and activate contact 140.

At the end of the power stroke, cam assembly 85 is rotated, aspreviously described, causing head 86 to mechanically abut shoulder 80.This lifts spring contact 74 off of contact 73, disconnecting power tocoil 25, thereby deenergizing the rotary solenoid. Before the returnstroke begins, however, the inertia of the system causes the rotor andhence cam 85 to continue to rotate, causing spring contact 74 to abutcontact 75 and connect positive voltage via contact 153, ring 150, leads142, ring segment 142 and contact 42 to terminal 136 of load L-1,electrically energizing the load. The load remains energized until theend of the return stroke, when cam assembly 85 is again rotated back toits initial position, causing spring 73 to return to contact 73.

When spring contact 74 again abuts contact 74, the abovedescribed cycleof operation is repeated. That is, coil 25 is energized, rotating therotor shaft and causing interruption of power to coil 25 and subsequentenergization of load L-2, after which the cycle is repeated for the nextload. Each of the loads L-1 through L10 is thereby energized for aprescribed period of time, controlled by various mechanical dimensionsof the switching assembly, including the length of the reciprocatingpath for link 22, FIG. 1, and the dimensions of cam 85.

After the last load L-10 has been energized, the switching assemblyrotates ring segment 142 adjacent home contact 43. Just prior to homecontact 43 grounding segment 142, stator contact 153 is disconnectedfrom ring 150 as segment 151 is rotated adjacent thereto. At the sametime, segment 158 of switch section 39 is rotated adjacent contact 52,thereby disconnecting contact 73 from connection with coil 25. Thus, thehome switch configuration prevents the DC source from again energizingcoil 25 as spring contact 74 returns to its normally closed positionagainst contact 73, precluding further electrical actuation of thecircuit.

The above-described circuit and switching assembly has many advantages.The circuit maintains all loads shunted across ground except for thesingle load which is being energized. This prevents stray electricalsignals or the like from accidentally being coupled to a different loadthan the one which is to be energized. The home position of theswitching mechanism and circuit requires manual actuation beforeelectrical actuation is possible, thereby providing a safety factor forpersonnel who must connect loads to the circuit.

Another advantage results from switch segments 37 and 39 beingelectrically separate from each other. In prior circuits forintervalometcrs of this type, a defective load, i.e., shorted, wouldresult in disabling of the self-completing stepping circuit. ln thepresent circuit, should a load be defective, the remaining loads are notthereby affected. DC source 130 desirably includes sufficient internalresistance means to prevent harm when a defective load presents a directshort to ground 132. Each time spring contact 74 returns against contact73, positive line 131 is connected to coil 25, irrespective of whetheror not the prior load presented a short to ground 132. This allows thestepping assembly to bypass the defective load. Many other advantageswill also be apparent to those skilled in the art.

1f manual rather than automatic self-stepping is desired, switch 161 isinitially closed. When switch 166 is thereafter closed, power isconnected as previously described to coil 25, causing a stepwisemovement of the switch. However, movement of contact 74 off of contact73 and against contact 75 no longer discontinues energization of coil25, due to the shunting action of switch 161. A load is energized in thesame manner as previously described, however, upon return of contact 74against contact 73, another stepping cycle is not initiated because coil25 has remained energized at all times. As contact 74 abuts contact 73,one cycle of operation is completed, with coil 25 still energized.

To initiate the next stepping cycle, the switch 166 is opened and thenagain closed, causing another power stroke to occur. Switch 166 may beof the momentary make type, in which the depression of a pushbuttoncloses the switch for a short period of time sufficient for contact 74to abut contact 75 and energize a load. For the purpose of automaticoperation, switch 166 should also have a locked closed position, so thatpower may be connected to the circuit for the whole cycle ofselfstepping energization of all loads. Thus, switches 161 and 166 allowselection of either automatic self-stepping or manual stepping of theswitching assembly.

We claim:

1. A rotary stepping assembly, comprising:

a drive assembly for reciprocating a member along a path for eachactuation of the drive assembly;

a stationary assembly having a base including at least one elongatedshaft permanently fixed to said base and extending outward therefrom,said shaft having guide means along at least its extended outer portion;

means mounting said drive assembly to said base;

a rotary assembly including stator means having stator contact meansthereon, rotor means mounted for rotation with respect to said statormeans and including rotor contact means aligned for contact with saidstator contact means at different rotary positions of said rotor means,means for converting reciprocating movement into stepwise rotarymovement of said rotor means with respect to said stator means, saidstator means further including first surface means abutting saidstationary assembly, second surface means adjacent the extended outerportion of said shaft, and channel means defining an opening betweensaid first and second surface means and through which said shaftextends;

fastening means connected to said guide means and abutting said secondsurface means for clamping said sta tor means to said stationaryassembly; and

link means connected between said drive assembly member and said rotaryassembly converting means for causing stepwise rotary movement for eachactuation of said drive assembly.

2. The rotary stepping assembly of claim 1 wherein said base comprises aplate having a lower surface defining a flat plane and an upper surfacewith a boss raised upward therefrom, said rotor means includes a rotorshaft and means mounting said rotor contact means for movement with saidrotor shaft, said boss includes a circular aperture of greater diameterthan the diameter of said rotor shaft, and means mounting said rotorshaft for rotatable movement within said circular aperture but with saidrotor shaft being raised above said flat plane of said plate.

3. The rotary stepping assembly of claim 2 wherein said rotor shaft hasan end portion extending upward from the upper surface of said plate,

said rotary assembly includes indicator means mounted to said endportion and manually actuable for stepwise rotating said rotor shaftindependent of stepwise movement produced by actuation of said driveassembly.

4. The rotary stepping assembly of claim 1 wherein said converting meansincludes a ratchet plate fixed with respect to said rotor means, saidlink means including a pawl engageable with said ratchet plate forconverting reciprocating movement of the link means into rotary movementof the ratchet plate, and spring means connected between said link meansand said stator means and compressible upon movement of said link meanscaused by actuation of said reciprocal drive assembly so that expansionof said spring means returns said link means to a rest position.

5. The rotary stepping assembly of claim 1 wherein the guide means onsaid elongated shaft comprises a screw, said fastening means comprisinga nut member threaded onto said screw so as to clamp said stator meansagainst said base.

6. The rotary stepping assembly of claim 5 wherein said elongated shaftincludes a portion adjacent said base and a portion of reduced diameterextending upward from said first portion, the surface of said elongatedshaft between said first portion and said reduced portion forming ashoulder lying in a plane normal to the axis of said elongated screw,said first surface means abutting said' shoulder and said nut memberabutting said second surface means for clamping said stator means tosaid stationary assembly in a position elevated above the base.

1. A rotary stepping assembly, comprising: a drive assembly forreciprocating a member along a path for each actuation of the driveassembly; a stationary assembly having a base including at least oneelongated shaft permanently fixed to said base and extending outwardtherefrom, said shaft having guide means along at least its extendedouter portion; means mounting said drive assembly to said base; a rotaryassembly including stator means having stator contact means thereon,rotor means mounted for rotation with respect to said stator means andincluding rotor contact means aligned for contact with said statorcontact means at different rotary positions of said rotor means, meansfor converting reciprocating movement into stepwise rotary movement ofsaid rotor means with respect to said stator means, said stator meansfurther including first surface means abutting said stationary assembly,second surface means adjacent the extended outer portion of said shaft,and channel means defining an opening between said first and secondsurface means and through which said shaft extends; fastening meansconnected to said guide means and abutting said second surface means forclamping said stator means to said stationary assembly; and link meansconnected between said drive assembly member and said rotary assemblyconverting means for causing stepwise rotary movement for each actuationof said drive assembly.
 2. The rotary stepping assembly of claim 1wherein said base comprises a plate having a lower surface defining aflat plane and an upper surface with a boss raised upward therefrom,said rotor means includes a rotor shaft and means mounting said rotorcontact means for movement with said rotor shaft, said boss includes acircular aperture of greater diameter than the diameter of said rotorshaft, and means mounting said rotor shafT for rotatable movement withinsaid circular aperture but with said rotor shaft being raised above saidflat plane of said plate.
 3. The rotary stepping assembly of claim 2wherein said rotor shaft has an end portion extending upward from theupper surface of said plate, said rotary assembly includes indicatormeans mounted to said end portion and manually actuable for stepwiserotating said rotor shaft independent of stepwise movement produced byactuation of said drive assembly.
 4. The rotary stepping assembly ofclaim 1 wherein said converting means includes a ratchet plate fixedwith respect to said rotor means, said link means including a pawlengageable with said ratchet plate for converting reciprocating movementof the link means into rotary movement of the ratchet plate, and springmeans connected between said link means and said stator means andcompressible upon movement of said link means caused by actuation ofsaid reciprocal drive assembly so that expansion of said spring meansreturns said link means to a rest position.
 5. The rotary steppingassembly of claim 1 wherein the guide means on said elongated shaftcomprises a screw, said fastening means comprising a nut member threadedonto said screw so as to clamp said stator means against said base. 6.The rotary stepping assembly of claim 5 wherein said elongated shaftincludes a portion adjacent said base and a portion of reduced diameterextending upward from said first portion, the surface of said elongatedshaft between said first portion and said reduced portion forming ashoulder lying in a plane normal to the axis of said elongated screw,said first surface means abutting said shoulder and said nut memberabutting said second surface means for clamping said stator means tosaid stationary assembly in a position elevated above the base.